Azure-native error when deploying SRE with DSH Pulumi

[dsj976]

✅ Checklist

• I have searched open and closed issues for duplicates.
• This is a problem observed when deploying a Data Safe Haven.
• I can reproduce this with the latest version.
• I have read through the documentation.
• This isn't an open-ended question (open a discussion if it is).

💻 System information

• Operating System:
• Data Safe Haven version: branch tresa-testing

📦 Packages

List of packages

Paste list of packages here

🚫 Describe the problem

I get the following error when running dsh sre deploy sandbox_sre:

Diagnostics:                                                                                                                        
  azure-native:operationalinsights:Workspace (sre_monitoring_log_analytics):                                                        
    error: azure-native:operationalinsights:Workspace resource 'sre_monitoring_log_analytics' has a problem: 'workspaceName' does   
not match expression '^[A-Za-z0-9][A-Za-z0-9-]+[A-Za-z0-9]$' 

🌳 Log messages

Relevant log messages

Your log details here

♻️ To reproduce

[jemrobinson]

This is caused by the use of underscores in the SRE name which need to be converted to - before they can be used as Azure resource names.